1990 Lincoln Towncar Bucks on starting & slowing

1990 Lincoln Signature Town Car, Auto Transmission, ? 2-wheel drive, 188,000 miles, engine replaced at 126,000 mi & transmission @ 128,000 in 1999 by prior owner. Car was a little sluggish on hills and acceleration, no noises, no bumps. Took in shop, found vacuum leak, replaced or repaired 2 valves: oxygen? And I/C (can’t find receipt). Told me I may have Fuel Injector problems (like years ago when 3 F/Is were replaced) because of bad air mix. Later replaced spark plugs, cap, rotor & wires (had 2 bad sets --maybe this one is bad?). Then tried 2 pressurized cleaning of Fuel Injectors & transmission service. Is Running as if on 4 valves at times, bucks worrisomely upon starting and until about 40mph and agaoin on slowing down. Ignition is also a bad/hard/noisy start (was replaced with used steering column 2 yrs ago). I hear a soft metal clanging occasionally, like the flaps on carburetors. There is uneven idling, only 1 or 2 small pops like backfires. It has gotten worse. When slowing down, I have to pump brakes to not have it feel like running over a corrugated roadway. Shop thinks (no real testing) that it’s transmission and Fuel Injectors. I haven’t had brakes done but have been asking for it for 6 months or so but other more necessary things had to be done. Spent about $1000 in 5 months... Including a new gas tank that has the pump inside it! They tell me to get a new car & junk this prior good -ride with New AC, tank, etc. I’d like to think it’s something simple they have over-looked.